Air control system for heating unit



Dec. 24, 1968 c. E. NELSON AIR comm. SYSTEM FOR HEATING UNIT 2Sheets-Sheet 1 Filed Feb. 9, 1967 N hhw INVENTOR. CHARL Est. NELsaNAvToRNEY;

Dec. 24, 1968 c. E. NELSON 3,417,977

AIR CONTROL SYSTEM FOR HEATING UNIT filed Feb. 9, 1967 2 Sheets-Sheet 2W UN a W DN 1 INVENTOR. CHARL Es fiNELsaN MM WW,

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United States Patent 3,417,977 AIR CONTROL SYSTEM FOR HEATING UNITCharles E. Nelson, Excelsior, Minn., assignor to Mammoth Industries,Inc., Minneapolis, Minn., a corporation of Minnesota Filed Feb. 9, 1967,Ser. No. 614,991

11 Claims. (Cl. 263-19) ABSTRACT OF THE DISCLOSURE An air flow controlsystem for a heating unit having a line direct fired gas burner.Movement of air around the burner is controlled by a pair of linearlymovable profile plates located adjacent the upper and lower sides of theshielding and mixing walls of the burner. The profile plates are part ofa system of dampers in the heating unit to regulate the ratio of freshair and return air discharged by the heating unit. A control unit ispart of a damper control system which selectively moves the profileplates to open and closed positions in conjunction with changing thepositions of fresh air intake damper blades and return air damper bladeswhereby a substantially constant velocity of air flows past the burnerto provide uniform firing characteristics.

Gas burners have been developed for direct fired operation in an airstream to heat the air in the stream and utilize part of the air of theair stream as a supply of air for combustion of gas discharged by theburner. Direct fired line burners of this type are arranged downstreamof the fresh air intake of the heating unit and heat fresh air flowingover the burner. These heating units are usually provided with fixedprofile plates to regulate the flow of air across the burner for aconstant amount of air. These profile plates are not closely correlatedwith the combustion area of the burner so as to effectively control theflow of varying amounts of air past the bumer. When used to change thevolume of air which flows past the burner rotating damper blades deflectand cause turbulence of the air flow causing incomplete combustion ofthe gases. An example of a direct fired line burner is shown in US.Patent No. 3,051,464.

Briefly described, the air control system of the present invention isused in conjunction with a line direct fired gas burner to maintain thevelocity of air flowing past the burner substantially constantregardless of the volume of the air flowing across the burner. Thecontrol system has a pair of movable doors or profile plates locatedadjacent the upper and lower sides of the mixing walls of the burner.The profile plates extended in a transverse direction relative to theflow of air across the burner do not deflect or cause turbulence of theflow of air thereby promoting uniform heating of air and completecombustion of the gases. The profile plates move in conjunction with themovement of dampers across the fresh air intake of the heating unit aswell as similar dampers across the return air duct whereby asubstantially constant amount of air flows through the heating unit atall times. The positions of the dampers and the profile plates areregulated by a control unit located in the room to be heated. Thecontrol unit is operable to change the percentage of fresh air relativeto return air from about 25% fresh air to 100% fresh air. The burner hasa separate control which at 25% or less fresh air it will automaticallyshut off whereby the heating unit circulates a mixture of unheated freshair and return air. With this control, a maximum amount of return airmay be circulated through the heating area during the non-occupiedperiods of a building.

In the drawings:

FIGURE 1 is a diagrammatic view of a fresh air heat- 3,417,977 PatentedDec. 24, 1968 See ing unit equipped with the air flow control structureof this invention;

FIGURE 2 is an enlarged sectional view taken along the line 22 of FIGURE1;

FIGURE 3 is an enlarged sectional view taken along the line 33 of FIGURE2 showing the profile plates on opposite sides of a linear direct firedburner in closed positions as at minimum fresh air flow through theheating unit; and

FIGURE 4 is a view similar to FIGURE 3 showing the profile plates inopen positions as at maximum fresh air flow through the unit.

Referring to the drawings, there is shown in FIGURE 1 a heating systemindicated generally at for supplying temperature controlled air to anenclosed space 11, as a room in a building. System 10 has a heatingunit, indicated generally at 12, which discharges air to a duct 13connected to space 11 and withdraws return air through duct 14 fromspace 11 into the heater unit.

Heating unit 12 is a furnace having a line direct fired burner indicatedgenerally at 16, such as the line burner disclosed in US. Patent No.3,051,464. Burner 16 has a transverse manifold 17 which carriesdiverging shielding and mixing walls 18 and 19 forming a transversemouth 21 which serves as a combustion chamber for the flame 22.Shielding and mixing walls 18 and 19 each have a plurality of openings23 and 24, shown in FIG- URES 3 and 4, for directing air into thecombustion chamber. Manifold 17 is coupled to a gas line 26 whichsupplies the gaseous fuel to the burner from a gas control unit 25.

As shown in FIGURE 2, control unit has a servo motor 25A connected to abutterfly-type valve 25B located in gas line 26. A line operativelycouples servo motor 25A with servo motor 61 used to change the positionsof the profile plates 48 and 49. In operation servo motor 61 sends asignal to motor 25A proportioning maximum gas supply to fresh airvolume.

Heating unit 12 has a housing or casing including a top wall 27 and abottom wall 28 which are separated at one end by fresh air intakeopening 29. A movable damper 31, as louvres or pivoted doors, extendacross fresh air intake opening 29 and are selectively moved to open andclosed positions by a servo motor 32. A linkage 33 operatively connectsthe servo motor with each of the damper doors. Fresh air indicated byarrows 34 flows past the doors through intake opening 29 toward theburner 16.

The movement of air past shielding and mixing walls 18 and 19 of theburner is controlled by an air flow control indicated generally at 36.In general, the air flow control 36 functions to maintain asubstantially constant volume of flow of air through the heater unitregardless of the ratio of fresh air and return air. This isaccomplished by controlling the ratio of fresh air to return air movinginto the heater unit in conjuction with changing the areas 37 and 38 onopposite sides of the shielding and mixing Walls 18 and 19 of the burnerwhich regulate the flow of air indicated by arrows 39 and 41 over theburner into air receiving chamber 42. As shown in FIGURE 1, heater unit12 has a blower 43 which circulates or drives the air through thehousing discharging air indicated by arrow 44 into the duct 13, drawingreturn air indicated by arrow 45 through the duct 14, and drawing freshair over burner 16. The amount of return air drawn into the heating unitis controlled by a movable damper 46, as louvers or pivotal doors,coupled by linkage 46A to a servo motor 47 operable to open and closedamper .46.

As best shown in FIGURES 3 and 4, control 36 includes a pair of movabledoors or profile plates 48 and 49 located adjacent opposite sides of theouter ends of the shielding and mixing walls 18 and 19 of the burner.Plates 48 and 49 are postioned in the same plane adjacent upright walls50 and 51 spaced from the shielding and mixing walls 18 and 19. Areas 37and 38 confine the fiow of air through the heating unit adjacentopposite sides of burner 16.

As shown in FIGURES 2 and 3, movable upper profile plate 49 hasrearwardly directed longtiudinal flanges 54 and 56 having aligned holesfor accommodating a plurality of spaced support rods 52 secured at theirlower ends to a transverse fiat beam 53. The opposite or upper ends ofthe rods 52 are mounted on frame structure on top wall 27. The lowerprofile plate 48 has similar flanges for accommodating a plurality ofspaced upright rods 57 which are secured at their upper ends to atransverse flat beam 58 and at their lower ends to a frame structuresecured on bottom wall 28. Rods 52 and 57 guide profile plates 49 and 48respectively for sliding movement in a common plane which is generallynormal to the flow of air passing through and moving over shielding andmixing burner walls 18 and 19. The plane of the profile plates 48 and 49is located in the general plane of the longi tudinal ends of theshielding and mixing walls 18 and 19.

A drive indicated generally at 59 including a servo motor 61 functionsto move profile plates 48 and 49 selectively toward and away fromopposite sides of burner 16 keeping areas 37 and 38 substantially equal.A linkage assembly indicated generally at 62 operatively couples servomotor 61 with the upper and lower profile plates so that the plates movetogether to simultaneously open or restrict areas 37 and 38. As shown inFIGURE 2, linkage assembly 62 has a transverse shaft or rod 63 rotatablymounted on a plurality of spaced upright brackets 64 carried on bottomwall 28. Secured to spaced portions of rod 63 are forward arms 66. Themiddle section of rod 63 carries an upright arm 67. The outer ends ofarm 66 are pivotally coupled to links 68 which are pivotally mounted toupper portions of lower profile plate 48 by a plurality of ears 70. Theouter end of upright arm 67 is pivotally connected to a link 69 used toconnect the outer end of a crank arm 71 secured to the drive shaft ofservo motor 61.

Secured to opposite ends of transverse rod 63 are rearward arms 72 and73 each carrying counterweights 74 and 76 at their outer ends to balancethe weight of lower profile plate 48. Counterweights 74 and 76 may belonger and heavier depending on the size of profile plate 48.

Movement of the upper profile plate 49 is controlled by a similarlinkage structure including a transverse rod or shaft 77 rotatablycarried on a plurality of spaced brackets 78 secured to top wall 27. Aplurality of forward projecting arms 79 secured to shaft 77 are eachpivotally coupled to links 81. The outer ends of links 81 are pivotallyconnected to brackets 82 secured to lower portions of upper profileplate 49. Shaft 77 is rotated in conjunction with the rotation of shaft63 by providing additional forwardly projecting arms 83 and 84 atopposite ends of rod 77 and coupling the forward portions of these arms83 and 84 to downwardly projecting rods 86 and 87. The lower ends ofrods 86 and 87 are pivotally attached to the outer ends of rearward arms72 and 73 respectively whereby rotation of shaft 63 in one directionresults in an equal and opposite rotation of shaft 77 in the oppositedirection. The weight of the upper profile plate 49 is balanced bycounterweights 88 and 89 carried on the outer ends of rearwardlyprojected arms 91 and 92 respectively mounted on the opposite ends ofshaft 77.

As indicated in FIGURE 3, arm 71 connected to the drive shaft of servomotor 61 is moved in the direction of the arrow 93 to move the profileplates 48 and 49 away from each other and increase the areas 37 and 38adjacent the walls 18 and 19 of burner 16. This increases the volume offresh air moving past the burner with the result that the ratio of freshair to return air is increased. Servo motor 61 is operable to hold theprofile plates at any position between the closed positions as shown inFIGURE 3 and the open positions as shown in FIGURE 4.

A control unit 94 located within the closed area, as a room, is used toconjunctively operate motor 32 to open and close the fresh air inletdamper 31, motor 50 to open and close the damper 46 located across thereturn air duct 14, and operate servo motor 61 to control the positionsof the profile plates 48 and 49. The control unit 94 operates motors 32,47 and 61 in conjunction with each other to maintain the flow of airthrough heating unit 12 at a substantially constant volume. The ratio offresh air to return air changes in proportion to each other so that thevolume of air moving through the heating unit is unaltered. Control unit94 is provided with a manually adjustable dial 95 movable for changingthe percentage of fresh air relative to return air from about 25% freshair and 75% return air to fresh air and no return air. At 25% fresh air,burner 16 will automatically shut off whereby the heating unit willcirculate return air mixed with unheated fresh air. This arrangementenables the enclosed area to have air circulation during periods, as anon-occupied period at nights, using the maximum amount of return air toreduce heating costs.

The linkages shown in the drawings conjunctively move profile plates 48and 49 toward and away from burner 16 in directions normal to the flowof air past the burner. These linkages are an example of one type ofpower transmitting structures which may be used to hold and change thepositions of the profile plates. Other power transmitting means as apair of screws having reverse threads driven by a reversible motor maybe used to move the profile plates. In a similar manner other controlledstructures for the fresh air intake damper 31 and return air damper 46may be used to move these dampers from their open and closed positions.

While there have been shown and described the novel features of theinvention as applied to a preferred embodiment it may be understood thatchanges may be made by those skilled in the art without departing fromthe spirit of the invention. The invention is limited only by the scopeof the following claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. In a heating unit having a direct fired burner, a fresh air intakeopening, first means for opening and closing the intake opening, areturn air passage, second means for opening and closing the airpassage, third means located adjacent opposite sides of the burner forcontrolling the velocity of air past the burner, and control meansoperable to change the relative positions of said first means, secondmeans and third means to change the ratio of fresh air to return airdischarged by the heating unit while maintaining a substantiallyconstant volume of air flowing through the heating unit and a constantvelocity of fresh air moving past the direct fired burner.

2. The heating unit of claim 1 wherein said burner has rearwardlydiverging transverse walls and said third means comprises fiat platesselectively movable toward and away from said walls in a directiongenerally normal to the flow of air past the burner.

3. The heating unit of claim 1 wherein the third means are profileplates selectively movable toward and away from the burner along a planegenerally normal to the flow of air past the burner.

4. The heating unit of claim 1 wherein the third means are profileplates, and rod means slidably mounting a profile plate on oppositesides of the burner for movement toward and away from the burner.

5. The heating unit to claim 1 wherein said control means includes afirst motor to move the first means to open and closed positions, asecond motor to move the second means to open and closed positions, athird motor to selectively move the third means toward and away from theburner, and a control to conjunctively operate all of said motors.

6. The heating unit of claim 1 wherein said burner has shielding andwalls and said third means comprises plates selectively movable towardand away from said walls.

7. The heating unit of claim 1 including means for controlling thesupply of gas to the burner in conjunction with the operation of thecontrol means to limit the maximum amount of gas supplied to the burnerin proportion to the amount of fresh air moving past the burner.

8. In a heating unit, a direct fired burner, first plate means on oneside of the burner, second plate means on the opposite side of theburner said first plate means and second plate means extended generallyparallel to the burner in planes generally normal to the flow of airpast the burner means mounting the first plate means and second platemeans for selected linear movement in opposite lateral directions insaid planes toward and away from the sides of the burner and controlmeans for moving the first plate means and second plate meansselectively toward and away from the sides of the burner.

9. The heating unit of claim 8 wherein the burner has rearwardlydiverging shielding and mixing walls having outer ends and said firstplate means and second plate means are spaced from and extend generallyparallel to the outer ends of said shielding and mixing walls.

10. The heating unit of claim 8 wherein the control means includes poweroperated means to conjunctively move the first plate means and secondplate means toward each other and away from each other.

11. The heating unit of claim 8 wherein the means mounting the firstplate means and the second plate means are rod means slidably mountingsaid plate means for movement toward and away from the burner.

References Cited UNITED STATES PATENTS 2,171,275 8/1939 Morrison 263-193,064,720 11/1962 Keating et al 263-l9 3,178,161 4/1965 Yeo et a1.263-49 3,199,848 8/1965 Harrison 126-110 CHARLES J. MYHRE, PrimaryExaminer.

E. G. FAVORS, Assistant Examiner.

